1. Field of the Invention
The present invention relates to a mold and method for producing a two-stroke engine casing, and more particularly to a mold and method for producing a two-stroke engine casing of a radio control model.
2. Description of Related Art
A conventional method for producing a two-stroke engine casing of a radio control model requires a core (71) to be separately received in a cavity (not shown) in a mold (not shown) for forming a cylinder in the engine casing. For forming three grooves in an inner periphery of the cylinder, with reference to FIG. 7, the core (71) has three channels (72) defined therein and extending to an outer periphery of the core (71). The three channels (72) respectively receive a first rod (73), a second rod (74) and a third rod (75). The first rod (73) has a first block (731) formed on an outer periphery of the first rod (73) and extending through the channel (72) in the core (71). The second rod (74) has a second block (741) formed on an outer periphery of the second rod (74) and extending through the channel (72) in the core (71). The third rod (75) has a third block (751) formed on an outer periphery of the third rod (75) and extending through the channel (72) in the core (71).
In molding, the core (71) with the first rod (73), the second rod (74) and the third rod (75) and other auxiliary cores (not shown) tire received in the mold and the melted material is injected into the mold. An engine casing is formed after the melted material is cooled and released from the mold. The core (71) and the rods (73, 74, 75) must be dipped in releasing agent because the core (71) and the rods (73, 74, 75) must be taken away from the engine casing. For a good releasing effect, the core (71) and the rods (73, 74, 75) are preheated to a high temperature before being dipped into the releasing agent. However, the above conventional mold and method has several disadvantages as follows.
1. The blocks (731, 741, 751) each has its own shape different from one another such that the blocks (731, 741, 751) need to be marked to prevent the blocks (731, 741, 751) from being mismatched, To mark the blocks (731, 741, 751) is trivial yet time consuming work which extends manufacturing time.
2. The rods (73, 74, 75) and the blocks (731, 741, 751) need to be preheated for good releasing effect, but the rods (73, 74, 75) and the blocks (731, 741, 751) are hard to mount in the mold when hot. The gain in releasing effect is diminished and the manufacturing time extended, where the rods (73, 74, 75) and the blocks (731, 741, 751) need to be cooled down for mounting.
3. The core (71) and the rods (73, 74, 75) are sequentially removed from the mold. However, the rods (73, 74, 75) are still engaged to the engine casing when the core (71) is removed from the mold. It is difficult to remove the rods (73, 74, 75) from the engine casing because the cylinder of the engine casing is usually of a small diameter, making cumbersome the removal of (the rods and their blocks (731, 741, 751) therethrough,
With regard to the above disadvantages, an improved mold and method for producing an engine casing is provided. With reference to FIG. 8, the mold includes a first core (81) having three grooves (82) defined in an outer periphery of the first core (81) and a hole (810) defined in a bottom of the first core (81). A second core (83) remains engaged with the first core (81) during molding. The second core (83) includes a stub (830) selectively received in the hole (810) in the first core (81), and three connectors (831) radially integrally extending from the stub (830) and selectively received in a corresponding one of the three grooves (82) in the first core (81). Each connector (831) has a block (832, 833, 834) integrally connected to a free end of a corresponding one of the three connectors (831).
The first core (81) is removed from the mold after molding. The blocks (832, 833, 834) automatically detach from the inner periphery of the cylinder when the connectors (831) are broken after the first core (81) is removed from the mold. Consequently, the manufacturing process and the releasing process are simplified. However, the problems relating to mounting the heated cores (81, 82) in the mold still have not been solved.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional molds and methods for producing a two-stroke engine casing of a radio control model.
The main object of the present invention is to provide an improved mold and method for producing a two-stroke engine casing of a radio control model.
To achieve the object, the mold and method for producing a two-stroke engine casing of a radio control model in accordance with the present invention include defining a core cavity and a main cavity in the mold. A first core has a first end inserted into the mold and, the core cavity is defined around the first end of the first core for forming a core, simplifying the manufacturing processes. The first core with the core is then inserted into the main cavity to form the cylinder of the engine and blocks formed on the core define grooves in the inner periphery of the cylinder of the engine.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.